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1. Reducing Native Ant Abundance Decreases Predation Rates in Midwestern Grasslands

   https://doi.org/10.1093/ee/nvz127  

   Wills, B D ; Kim, T N ; Fox, A F ; Gratton, C ; Landis, D A ; Redak, Richard ( November 2019 , Environmental Entomology)

   Abstract Diverse and robust predator communities are important for effective prey suppression in natural and managed communities. Ants are ubiquitous components of terrestrial systems but their contributions to natural prey suppression is relatively understudied in temperate regions. Growing evidence suggests that ants can play a significant role in the removal of insect prey within grasslands, but their impact is difficult to separate from that of nonant predators. To test how ants may contribute to prey suppression in grasslands, we used poison baits (with physical exclosures) to selectively reduce the ant population in common garden settings, then tracked ant and nonant ground predator abundance and diversity, and removal of sentinel egg prey for 7 wk. We found that poison baits reduced ant abundance without a significant negative impact on abundance of nonant ground predators, and that a reduction in ant abundance decreased the proportion of sentinel prey eggs removed. Even a modest decrease (~20%) in abundance of several ant species, including the numerically dominant Lasius neoniger Emery (Hymenoptera: Formicidae), significantly reduced sentinel prey removal rates. Our results suggest that ants disproportionately contribute to ground-based predation of arthropod prey in grasslands. Changes in the amount of grasslands on the landscape and itsmore »management may have important implications for ant prevalence and natural prey suppression services in agricultural landscapes.« less
2. An observation of a potentially novel defensive behavior against pesticides: Messor oertzeni build a defensive wall against ant traps in the field (preliminary note)

   PRETENDS EAGLE, TJ: RODRIGUEZ ( October 2021 , Bulletin of insectology)

   In the course of conducting honey bee experiments on the Greek Island of Lesbos we took the opportunity to observe the reactions of ants, Messor oertzeni Forel (Hymenoptera Formicidae Myrmicinae), to a baited ant trap placed in its main foraging path (active ingredient: sodium cacodylate). Each trap had three entrances and we tested five nests. For 14 days we observed the nests and photographs were taken daily to document our observations. Following a baseline condition in which none of the three entrances were open, one entrance was open. Several days later the entrance we opened was turned 90 degrees away from the main foraging trail and a second entrance was opened and placed in the same orientation as the first entrance (i.e., in the main foraging path). Our observations revealed that for four of the five ant colonies, the ants built a barrier around the opened entrance preventing other ants from entering the trap. The materials they used to bar the entrance was composed of twigs, pebbles and soil. We believe that the apparent ability of ants to avoid the effects of an insecticide by baring the entrance to a bait trap is a novel finding and should be replicatedmore »under more controlled conditions.« less
3. Time-course RNASeq of Camponotus floridanus forager and nurse ant brains indicate links between plasticity in the biological clock and behavioral division of labor

   https://doi.org/10.1186/s12864-021-08282-x  

   Das, Biplabendu ; de Bekker, Charissa ( January 2022 , BMC Genomics)

   Circadian clocks allow organisms to anticipate daily fluctuations in their environment by driving rhythms in physiology and behavior. Inter-organismal differences in daily rhythms, called chronotypes, exist and can shift with age. In ants, age, caste-related behavior and chronotype appear to be linked. Brood-tending nurse ants are usually younger individuals and show “around-the-clock” activity. With age or in the absence of brood, nurses transition into foraging ants that show daily rhythms in activity. Ants can adaptively shift between these behavioral castes and caste-associated chronotypes depending on social context. We investigated how changes in daily gene expression could be contributing to such behavioral plasticity inCamponotus floridanuscarpenter ants by combining time-course behavioral assays and RNA-Sequencing of forager and nurse brains.

   We found that nurse brains have three times fewer 24 h oscillating genes than foragers. However, several hundred genes that oscillated every 24 h in forager brains showed robust 8 h oscillations in nurses, including the core clock genesPeriodandShaggy. These differentially rhythmic genes consisted of several components of the circadian entrainment and output pathway, including genes said to be involved in regulating insect locomotory behavior. We also found thatVitellogenin, known to regulate division of labor in social insects, showed robust 24 h oscillations in nurse brainsmore »but not in foragers. Finally, we found significant overlap between genes differentially expressed between the two ant castes and genes that show ultradian rhythms in daily expression.

   This study provides a first look at the chronobiological differences in gene expression between forager and nurse ant brains. This endeavor allowed us to identify a putative molecular mechanism underlying plastic timekeeping: several components of the ant circadian clock and its output can seemingly oscillate at different harmonics of the circadian rhythm. We propose that such chronobiological plasticity has evolved to allow for distinct regulatory networks that underlie behavioral castes, while supporting swift caste transitions in response to colony demands. Behavioral division of labor is common among social insects. The links between chronobiological and behavioral plasticity that we found inC. floridanus, thus, likely represent a more general phenomenon that warrants further investigation.

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4. A taxonomic revision of the Malagasy endemic subgenus Mayria of the genus Camponotus (Hymenoptera, Formicidae) based on qualitative morphology and quantitative morphometric analyses

   https://doi.org/10.3897/zookeys.1081.71872  

   Rasoamanana, Nicole ; Fisher, Brian L. ( January 2022 , ZooKeys)

   The subgenus Mayria of the genus Camponotus (Hymenoptera: Formicidae) is revised. The subgenus is endemic to Madagascar where it occupies a broad range of habitats, from deciduous and dry forest to rainforest. A taxonomic review is provided of this subgenus, integrating multiples lines of evidence including qualitative morphology and quantitative morphometry. Species hypotheses are formed by Nest Centroid clustering. In total, 36 species are treated, of which eleven are newly described: Camponotus andrianjaka sp. nov. , Camponotus antsaraingy sp. nov. , Camponotus chrislaini sp. nov. , Camponotus claveri sp. nov. , Camponotus ivadia sp. nov. , Camponotus jjacquia sp. nov. , Camponotus maintilany sp. nov. , Camponotus norvigi sp. nov. , Camponotus ihazofotsy sp. nov. , Camponotus tsimelahy sp. nov. , Camponotus zoro sp. nov. Five species are redescribed. Camponotus themistocles Forel stat. nov. , is raised to species. In addition, the subgenus is redefined to include 39 species. Twenty-two previously described species are transferred to this subgenus and thirteen species previously placed in the subgenus are transferred out of the subgenus. Nine morphologically consistent species groups are delineated to facilitate species identification within the subgenus. This revision includes a classification, a key to species groups, and an updated keymore »to species based on the minor worker caste.« less
5. Automated tracking and analysis of ant trajectories shows variation in forager exploration

   https://doi.org/10.1038/s41598-019-49655-3  

   Imirzian, Natalie ; Zhang, Yizhe ; Kurze, Christoph ; Loreto, Raquel G. ; Chen, Danny Z. ; Hughes, David P. ( September 2019 , Scientific Reports)

   Determining how ant colonies optimize foraging while mitigating pathogen and predator risks provides insight into how the ants have achieved ecological success. Ants must respond to changing resource conditions, but exploration comes at a cost of higher potential exposure to threats. Fungal infected cadavers surround the main foraging trails of the carpenter antCamponotus rufipes, offering a system to study how foragers behave given the persistent occurrence of disease threats. Studies on social insect foraging behavior typically require many hours of human labor due to the high density of individuals. To overcome this, we developed deep learning based computer vision algorithms to track foraging ants, frame-by-frame, from video footage shot under the natural conditions of a tropical forest floor at night. We found that most foragers walk in straight lines overlapping the same areas as other ants, but there is a subset of foragers with greater exploration. Consistency in walking behavior may protect most ants from infection, while foragers that explore unique portions of the trail may be more likely to encounter fungal spores implying a trade-off between resource discovery and risk avoidance.